As will be appreciated by those familiar with vehicular propulsion systems, such systems are desirably highly efficient and emit to the atmosphere low levels of pollutants. However, known systems which attempt to conform to these requirements are characterized by extremely high cost of manufacture, excessive weight, costly maintenance and/or inconvenience to the user.
Accordingly, the primary object of the present invention is to provide an improved propulsion system, particularly for a vehicle, which is low in cost, efficient in operation, and emits only a minimum of pollutants.
A further object is to provide a propulsion system using only a single main reciprocating part which acts both as a piston for an internal combustion engine and as a piston for a hydraulic pump, which combination is hereinafter referred to as an engine-pump unit.
A still further object of the invention is to provide an engine of the so called free-piston type, which engine includes means for supplying the necessary fuel and air to the engine so as to ensure efficient yet self-sustained operation of the engine.
Another object of the invention is to provide control means which permit starting and restarting of the engine-pump unit in a simple and efficient manner until the reciprocating movement of the engine is self-sustained.
It is also an object of the invention to provide a propulsion system, as aforesaid, incorporating an improved means of pumping hydraulic fluid in association with an internal combustion engine, whereby the hydraulic fluid functions as a medium for driving a vehicle.
A further object of the invention is to provide an improved fuel injection system for use with a free piston engine-pump unit, and in particular a simple fuel-injection system which uses the motion of the engine or pump piston for providing the impetus for both injecting the fuel and controlling the amount of fuel so injected, both as a function as the time interval between engine cycles and the pressure of the hydraulic fluid being pumped.
Still a further object of the invention is to provide a control system, specifically a cycling change valve assembly, for association with the engine-pump unit to permit efficient and simple startup of the unit by reversing the flow of hydraulic fluid to the pump pistons so as to drive the free piston assembly up to speed until self-sustained operation by virtue of fuel combustion can be achieved.
It is also an object of the invention to provide an improved scavenge valve system associated with the engine-pump unit, which scavenge valve system uses the cyclically varying hydraulic pressures for actuating the scavenge valves, and which system also provides for proper actuation of the scavenge valves during startup of the engine-pump unit.
Other objects and purposes of the present invention will be apparent to persons acquainted with systems of this general type upon reading the following specification and inspecting the accompanying drawings.